For ADHD, based on a case-control study completed several years ago in a local school district, we have published a manuscript on ADHD prevalence among elementary school children. Using our epidemiologic case definition, 15.5% of children in grades 1-5 in this school district had ADHD. Though higher than many estimates, ours is based on systematic screening of all children in the schools and so captures children who may not be evaluated in studies involving clinical diagnoses. Future work will address maternal stress during pregnancy as a possible risk factor for ADHD. (see Z01 ES49034; PI Dale Sandler, EB) In ongoing work on ALS, we are examining military and occupational exposures as risk factors in collaboration with researchers at Duke University and the Durham Veterans Administration Hospital using data from a case-control study of U.S. veterans. (see Z01 ES49005; LI Freya Kamel, EB) We have carried out a case-control study nested within the Agricultural Health Study to examine associations between Parkinson's disease and environmental risk factors, particularly certain pesticide exposures. We are also looking at selected candidate genes as susceptibility factors. This study employs data from the Agricultural Health Study as well as additional questionnaire data and field samples collected expressly for this effort. We have reported that the risk of Parkinson's disease associated with paraquat increases dramatically when the subject carries a homozygous deletion of the glutathione-S-transferase gene GSTT1 . We have observed that higher intake of N-3 polyunsaturated fatty acids was associated with lower risk of PD in general and appeared to lower the PD risk associated with paraquat use. We are investigating whether polymorphisms in genes coding for peptidoglycan recognition proteins are associated with PD. Analysis of data is ongoing. (see Z01 ES44007 EB; LI Freya Kamel, EB) Data collection for a study of the effects of soy estrogen on neonatal development is underway at Childrens Hospital of Philadelphia. We are currently working with two commercial laboratories and the CDC to resolve some inter-laboratory differences in testosterone measurements. We have published a paper characterizing the performance of methods for cytological assessment of vaginal and urethral epithelium in infants. (see Z01 ES44006 EB; PI Walter Rogan, EB) A recently initiated effort will be using data from the Medical Birth Registry of Norway to estimate the gestational-age-specific risk of stillbirth among mothers with and without preeclampsia.